My patent application Ser. No. 831,170, filed Sept. 7, 1977 for "Sulfur Removal from Coal" is directed to reducing the sulfur content of coal by drying coal particles and subjecting a mixture thereof with hydrogen to microwave energy. My patent application Ser. No. 831,171, also filed Sept. 7, 1977, for "Shale Conversion Process," is directed to converting the kerogen of shale to oil products by drying the shale and subjecting a mixture thereof and hydrogen to microwave energy. My patent application Ser. No. 896,003, filed Apr. 13, 1978 for "Process for Removing Sulfur from Coal," is directed to reducing the sulfur content of coal by forming a slurry of coal particles in an inert solvent, and subjecting the slurry in admixture with hydrogen to the influence of wave energy in the microwave range.
The present invention relates to a process for regenerating spend solid particles which have been deactivated in a process for cracking petroleum hydrocarbons, usually petroleum fractions boiling above about 400.degree. F., say within the range of from about 500.degree. F. to about 1100.degree. F., in a fluidized cracking process. In fluid catalytic cracking, a charge stock is contacted with a fluidized catalyst under conditions such that the charge stock is converted at least in part to lower boiling, more valuable products, usually gasoline, fuel oil, and the like. In the cracking process, the catalyst becomes deactivated through the deposition of carbonaceous materials on the surface thereof. Such carbonaceous materials, designated "coke," are highly condensed aromatic materials containing some hydrogen and sulfur and nitrogen compounds, believed in a total amount of from about 0.5 to 1.5% by weight, which amount deactivates the catalyst so that regeneration becomes economically desirable. For convenience this deactivating material is referred to herein simply as "coke." It is normal practice to include in the cracking procedure a regeneration step for burning deactivating coke from the catalyst. Usually a stream of catalyst is removed from the reactor, stripped to remove at least a portion of the volatile hydrocarbons, and is introduced into a regenerator together with air, which burns a major portion of the coke to oxides of carbon. The regenerated catalyst is then reintroduced into the reactor.
Many catalytic cracking units are limited by coke burning facilities, since the construction of the regeneration section of the cracking unit represents a major part of the capital cost. Thus, any increase over normal coke formation which may be experienced, such as may be caused by basic nitrogenous compounds in the feed, metal contamination of the catalyst, or any formation of a coke more refractory, i.e., more resistant to burning than expected, may require that the feed rate introduction be reduced significantly. Also, the practice of burning the coke with air in effect is a loss of valuable petroleum hydrocarbons to oxides of carbon.
An object of the present invention is to provide a novel process for regenerating spent cracking catalyst in a facile and economical manner.
A specific object of this invention is to provide a process for removing coke from cracking catalyst in which the coke is converted to valuable products.
Another object is to reduce the time required for regenerating cracking catalyst, i.e., to reduce the residence time of the catalyst in a regeneration vessel, whereby the capital cost of the regenerator section of a cracking unit can be reduced.
In an embodiment of the invention, deactivated fluid cracking catalyst is passed from the cracking reactor to the regenerator as is common practice, except that hydrogen is introduced with the catalyst particles instead of air, and the catalyst particles fluidized with hydrogen are subjected to energy in the microwave range. The coke is converted to volatile products and removed with the hydrogen, and regenerated catalyst is returned to the reactor.
In another embodiment of the invention, deactivated catalyst is removed from the reactor, admixed with a solvent which serves as the liquid medium to form a slurry, and the slurry containing dissolved hydrogen is subjected to energy in the microwave range. The deactivating coke is converted to products soluble in or miscible with the solvent, and regenerated catalyst is separated and returned to the reactor, or the slurry containing reactivated catalyst can be introduced into the reactor where the solvent is an appropriate feed stock to the catalytic reactor.
The accompanying Figure is a schematic flow diagram illustrating preferred embodiments of the process of the invention and will be described in detail hereinafter.